Primary arthroplasty of infected hips and knees in special cases using antibiotic-loaded bone-cement for fixation.

As a consequence of successful 1-stage exchange of infected joint prostheses, we decided to treat bacterial infection of the hip or knee by joint resection, synovectomy, and primary implantation of a hip or stabilized knee prosthesis. Since 1984, we have performed this procedure on 51 hips and 32 knees. All operations were preceded by identification of the causative organism and choice of appropriate antibiotics for addition to the bone-cement. The long-term rate of success corresponds to that of 1-stage exchange of infected prostheses. The different anatomic conditions at the hip and knee have to be taken into consideration. This treatment is restricted to special cases and should be performed only in specialized clinics with competent assistance from a bacteriologist.

Ionogran in revision arthroplasty.

Glass ionomer cement (Ionocem) was developed for use in bone surgery and is reported to be notably biocompatible. Between 1991 and 1994 we performed revision operations for aseptic loosening of arthroplasties of the hip on 45 patients using this material in its granulate form (Ionogran) mixed with homologous bone as a bone substitute. Of these 45 patients, 42 were followed up for a mean of 42 months. Early reloosening of the acetabular component has occurred in ten after a mean of 30 months. Histological examination showed large deposits of aluminium in the adjacent connective tissue and bone. Osteoblastic function and bone mineralisation were clearly inhibited. The serum levels of aluminium were also increased. The toxic damage at the bone interface caused by high local levels of aluminium must be seen as an important factor in the high rate of early reloosening. Our findings cast doubt on the biocompatibility of this material and we do not recommend continuation of its further use in orthopaedic surgery.

Wear in retrieved condylar knee arthroplasties. A comparison of wear in different designs of 280 retrieved condylar knee prostheses.

The plastic components of 280 retrieved unicondylar and total knee arthroplasties were studied. Wear was visually scored using a relative ranked data method. Although wear on the components was highly variable, several conclusions could be drawn regarding the nature and causes. Wear was associated more with the medial than the lateral condyle. Delamination was the most severe type of wear and occurred in short (< 5 year)-, medium (5-10 years)-, and long (> 10 years)-term retrievals. In the short term, delamination wear was associated with hot pressing of the tibial plastic or with fracture of the tibial baseplate. For a single design, a significant difference in the amount of delamination on hot-pressed and non-hot-pressed tibial components was observed. In medium- and long-term retrieved specimens of the designs with moderately high conformity, delamination wear was associated with restriction of rotational movement of the femoral component or with abrupt changes in the radius of the tibial component. In flatter, less conforming designs, wear was associated with laxity, such that the polyethylene delaminated toward the edges of the tibial component. Wear attributed to cement abrasion or entrapment occurred on the more conforming designs. Delamination was associated with the presence of fusion defects in the polyethylene but could also occur in the absence of such defects. That delamination was the principal were type and that this is caused by a fatigue mechanism mean that the incidence of failure could accelerate considerably over follow-up periods beyond 10 years. Designs of moderate conformity without abrupt changes in radii may prolong the duration of plastic tibial components before serious delamination occurs.

[Total hip endoprosthesis following resection arthroplasty]. / Totale Hüftendoprothese nach Resektionsarthroplastik.

From 1976 to December 1994, a total of 347 patients underwent implantation of a hip prosthesis at the ENDO-Klinik for treatment of an unsatisfactory condition following resection arthroplasty. From 1976 to 1987, 143 patients were treated and in 1989 the results obtained in these patients were analysed: 99 of them were available for a follow-up examination in 1989, and 64 for a further examination in 1995. In 130 cases infection had been the reason for joint resection. At the time of the prosthesis operation (1-20 years later) intraoperative biopsy revealed that infection was still present in 41 cases (31.5%). Only 15 of these infections had been detected preoperatively by joint aspiration. This shows that the value of resection arthroplasty as a method of treating periprosthetic infection is limited and lends support to the one-stage exchange operation, which is the method we prefer in cases of infected hip prostheses. The operative technique and preparation for implantation of the prosthesis are described, as are septic and aseptic complications and the measures that can be taken to treat them. In spite of the patients' generally poor initial condition and with due consideration for the further revision operations, the medium-term results finally obtained are poor in only 9%.

[Intraoperative leg length measurement in total hip endoprosthesis]. / Intraoperative Beinlängenmessung bei totaler Hüftendoprothese.

Preservation or restoration of the equal length of both legs after total hip arthroplasty is best achieved by direct intraoperative measurement. The measuring instruments designed for this purpose are presented and their application described for the posterior approach to the hip. The instruments are easy and quick to use. They can also be used for other approaches to the hip and in addition they are a valuable aid when estimating the angles of anteversion and inclination of the acetabular component. The high degree of accuracy and the significant improvement in results when this instrument was used intraoperatively was confirmed by comparison of radiographic measurements of two operation series.

Polyethylene wear in unicondylar knee prostheses. 106 retrieved Marmor, PCA, and St Georg tibial components compared.

106 unicondylar knee replacement tibial components were retrieved and analyzed for the amount and type of polyethylene wear. Three different designs were retrieved which had essentially the same femorotibial conformity. Each design showed a characteristic failure pattern. The polyethylene of PCA tibial components showed serious delamination after only short durations, as a result of heat pressing. St Georg sledge prostheses showed some delamination after 4 years' duration due to sub-surface cracks which were initiated by fusion defects in the polyethylene; metal backing of the components did not affect delamination of this prosthesis. The Marmor designs showed the least wear, with shiny depressions and surface pitting; no delamination was observed in the Marmor prosthesis. Molecular weight determination by gel permeation chromatography and analysis of crystallinity using Fourier transformation infra-red spectroscopy demonstrated that St George polyethylene had higher molecular weight and crystallinity than Marmor polyethylene. In some of the components investigated, crystallinity and molecular weight of the polyethylene were reduced under the wear track when compared with the unworn polyethylene. Since fusion defects may cause delamination of polyethylene we urge manufacturers to reduce the number of such defects.

The saddle prosthesis for salvage of the destroyed acetabulum.

We report the 12 to 74 month results of our mark I saddle prosthesis after its use as a salvage device for gross loss of pelvic bone stock in 76 patients with failed hip arthroplasties. The implant transmits load between iliac bone and bare polish chrome-cobalt. Our clinical and radiological results indicate that a useful and stable articulation can be achieved in most cases, provided that continued deep infection can be avoided. The appearance of radiological sclerosis at the bearing site in successful cases seems to indicate that significant late migration will not occur. Based on our experience with the mark I prosthesis we have designed and developed a mark II model which has freedom of axial rotation of the saddle. Our early results in 40 cases show a significant improvement over the results which could have been predicted for the mark I device.

[A quantitative analysis for determining porosity of pre-compressed and vacuum-mixed bone cement]. / Eine quantitative Analyse zur Bestimmung der Porosität von vorkomprimiertem und unter Vakuum gemischtem Knochenzement.

The porosity and the mechanical strength of 64 bone cement specimens were investigated. Different types of mixing procedures were tested: 1) hand, 2) compression, 3) vacuum and 4) the combination of vacuum stirring and compression. The differences in porosity and mechanical stability are remarkable. In relation to hand-mixed bone cement all techniques are leading to a reduction in the number of cavities. Specimens made by compression are showing a confluence of several small cavities to a few large. There is only a change in the distribution of the embedded gas volume, but not a reduction. The lowest porosity is seen in vacuum mixed specimens.

[Complications following hip joint prosthesis]. / Komplikationen nach Hüftgelenksendoprothesen.

Complications seen after long-term follow-up examinations of total hip replacement should be treated immediately and completely. In the past decade a considerable increase in revisions has been noted. Radiographic assessment may be regarded as an effective means in diagnosing prosthetic complications from the surgeon's point of view. Examples are given. The difficulties in radiographic assessment of complications after cementless implantation or cemented prostheses without contrast media are mentioned. Prosthesis-related complications, such as mechanical loosening, infection with and without loosening, fatigue fractures and wear, fractures of the femur or pelvis, dislocations and surgical failures, are illustrated, as are clinical courses with gross loss of bone stock after repeated surgery and delayed revisions. Complications not related to the prosthesis such as periarticular ossification, muscle deficiencies, and nervous and vascular lesions are also explained using examples.

[Long-term comparison of the "St. Georg" knee endoprosthesis system. 10-year survival rates of 2,236 gliding and hinge endoprosthesis]. / Langzeitvergleich der Knie-Endoprothesensysteme "St. Georg". 10-Jahres-Uberlebensraten von 2236 Schlitten- und Scharnier-Endoprothesen.

A comparison of results between the total hinge and the sled prosthesis "St. Georg" has revealed significantly inferior results for the sled prosthesis due to a greater number of aseptic loosenings predominantly of the tibial component, primary and secondary laxity of ligaments and/or residual pain, e.g. due to malposition. The 10-years survival rate for the total hinge prosthesis was 94 per cent, thus exceeding the results obtained in total hip arthroplasty. The disadvantages of the rigid hinge models, as for instance unphysiological support and guidance and insufficient cushioning during knee motion have been compensated for in our modification, the "Endo" rotational knee prosthesis. The indications for a surface knee replacement are restricted to cases with an intact ligamentous apparatus and unicondylar arthrosis.

[The interposition nail in diaphyseal bone defects and arthrodesis nail in failed knee-joint replacement]. / Interpositionsnagel bei diaphysären Knochendefekten und Arthrodesenagel bei gescheitertem Kniegelenksersatz.

Our clinical experience with different constructions of interposition and arthrodesis nails, used in 3 and 12 patients respectively, is presented. It has shown that cemented intramedullary nailing for the stabilization of long bones and the knee joint using an approach from the site of the defect is a useful additional means in reconstructive bone and joint surgery.

[Bone and boundary zone changes following the implantation of double-cup arthroplasties]. / Knochen- und Grenz schichtveränderungen nach Implantation von Double-Cup-Arthroplastiken.

21 femoral heads of 20 patients with double cup arthroplasty were examined after an implantation period of 1 to 5 years, in one case after 18 years. In 8 cases the hipe socket and in 10 cases the femoral cup became loose. Therefore an operative removal was necessary. 2 patients showed extensive periarticular ossifications. In connection with the metal cup the resected femoral heads were cut in slices of 1 cm. thickness. After taking an X-ray they were embedded without decalcification in methylmetacrylate. The sections were stained with different methods (Goldner, v. Kossa modification). In the group with fixed cup a local osteoporosis is dominating. The fibrous tissue membrane between cement and bone tissue is varying in thickness. It is thicker at the periphery of the cup. In the group with loosened cups large irreparable bone necrosis with included histiocytic granulomas, could be observed. The clinical problems are discussed in accordance to the long term prognosis on the basis of the morphological results.

[Modular system for the total replacement of the femur--Endo-model]. / Modulares System für den Femurtotalersatz--Endo-Modell.

Total femur replacement may offer a useful solution in cases of severe trauma or neoplasia and in revision arthroplasty after failed total joint replacement when gross losses of bone have resulted in an unloadable femur and all other methods of treatment would fail to provide the patient with a stable leg. Until recently, total femur components were custom-made, but now we have a comprehensive modular total femur implant available reducing problems of preoperative preparation and simplifying the manufacture of custom-made designs. The new device can be shaped and adapted to the conditions encountered at the time of operation. The "push-through" type of prosthesis can be mounted step by step and converted into a total femur replacement with either a conventional head or a saddle at the proximal end and a total axial rotating knee prosthesis at the distal end. Elongation of the entire system is feasible.

The total femoral prosthesis. A preliminary report.

The use of a total femoral prosthesis can offer a realistic alternative to amputation or disarticulation. The limited indications for such a prosthesis in the surgical management of primary bone tumours and pathological fractures still exist. In this specialised clinic there is an increased need to replace the entire femur where repeated procedures have failed, from loss of bone stock with infection or because of non-union in the presence of a prosthesis. Over the past eight years, four basic models have been developed. The most recent designs allow for the preservation of non-involved bone or for stable support where there is complete acetabular destruction.